The field of this invention is one-way or check valves.
It is often necessary to utilize "through conduit" or "station venturi" check valves to control the direction of fluid flow in pipelines. Such valves permit only uni-directional fluid flow and are actuated by the direction of the fluid flow. When the valves are open, they provide open flow passages to allow passage of pipeline pigs, balls, or the like, and cause little interference with the normal fluid flow through the pipeline. In addition, it is highly desirable that the valves be constructed in such a manner that installation and replacement can be accomplished within minimal expenditures of time, labor and money.
In the past, check valves such as those described in U.S. Pat. Nos. 2,882,923; 3,191,619; and 3,720,225 were available. However, several problems were associated with such valves. For example, they required an enlarged area in the valve body to permit the pivotally mounted clapper to swing freely. This enlarged area caused a drop in the pipeline pressure and interfered with the normal fluid flow through the pipeline. Recesses at the bottom of the valve bodies caused fluid turbulence which also interfered with the normal fluid flow in the pipelines. Further, none of the known valves was constructed so that it could have been easily installed between portions of the pipeline having flow conduits of the equal size. The bodies of some of the valves had to be shaped to conform to particular flange designs, others required the use of pipe flanges having a unique design, and most necessitated the performance of welding, press-fitting, or sweating operations during the installation process.